This invention pertains to a read-out system for use in conjunction with a wheel balancing machine.
As is known, wheel balancing machines, for example, of a type shown in U.S. Pat. No. 3,910,121 include means for mounting a wheel upon a shaft to be rotated therewith. While the wheel and shaft are being rotated suitable sensors serve to detect the angular location and amount of weight to be added at the "balance point" in order to balance it. In apparatus of the kind described the wheel is subdivided into a predetermined number of angular positions. In one instance the wheel is subdivided into fifty angular positions identified by each of a series of fifty numbers formed and distributed around a hub portion which rotates with the shaft carrying the wheel. The detected angular position is displayed to the operator as a number between 00 and 49. To locate the balance point the operator notes the detected position number (i.e. 00-49) appearing in the visual display. This number denotes the number on the hub to be aligned with a predetermined reference for a stationary portion of the machine thereby registering the balance point at such reference. This reference preferably coincides with top dead center of the wheel so that weights can be applied at that location. Accordingly, position displays associated with such a system have necessaryily displayed two orders of digits, i.e. 00-49 and have required the operator to note the angular position number displayed and then register that number (carried by the hub) with the reference.
According to the present invention the need for operator comparison between the displayed position and the wheel position has been eliminated.
In fact, the predetermined reference is not a visible marking at all, but is merely a predetermined rotational position, such as top dead center (TDC). Thus, when the "balance point" of the wheel has been properly rotated into coincidence with the reference it will be at TDC so that the weights can be more easily applied. While reference has been made to the "balance point" of the wheel there are actually two "balance points", one for the plane of each rim and weight is preferably applied to each rim, normally at different angular positions from each other. However, for simplicity reference to a balance point of "the wheel" is believed not to be misleading.
Simply stated as disclosed herein (and after the "balance point" for the wheel has been detected) the system is arranged whereby as the wheel is rotated the angular displacement defined between the "balance point" and a predetermined reference relative to a stationary portion of the machine is represented on a display which varies as the wheel is rotated until the display indicates coincidence between the reference and the balance point. Weight can then be applied to the wheel at that position.
In addition, according to a preferred embodiment, the system is made more sensitive around the "balance point" by employing a first scale associated with the rotational position of the wheel and converting it to a second scale such as a non-linear scale associated with the read-out display means. In this way wheel position can be represented (in one embodiment) by a single digit whose value is reduced to zero at a non-linear rate as the wheel is turned to cause coincidence between the balance point position on the wheel and a predetermined reference position for a stationary portion of the machine.